Definitely get the action of the guitars properly set up. It's amazing how much it can often improve the playability of a guitar, even (especially!) one that's right out of the chute.

I use a classic mostly, so I use an old-fashioned wooden çejilla (seh-HEE-yah). CLICKY. Flamenco guitarists use them a lot. Not too practical for a steel-string guitar, though.

On my steel-string, I use a Shubb. CLICKY #2. They work like a charm, don't scratch the guitar unless you get very clumsy with them, and they come in nickel or brass, and you can get them straight (for a classic) or slightly curved (for a steel-string).

Except for the çejilla on my classic, they're the best capos I've ever found.

'Course, if nothing else works, there's always THIS.

Don Firth

P. S.   Piece of trivia, perhaps, but if you're ever on Jeopardy and the question comes up:   The word "capo" is short for "capotasto," which is Italian. "Capo" means "head," and "tasto" refers to the key of a musical instrument. So essentially it translates into "head key." The device was invented sometime in the 1700s. CLICKY.

Sometimes you see a guitar capo referred to as a "capo d'astro." No, no, no! A capo d'astro is a part in some brands of grand pianos (Bösendorfer, for one), which alters to tone (presumably, enriches it), but does not change the pitch of a piano's strings. Totally different function from a capotasto.

More that you ever wanted to know.